(a) Technical Field
The present invention relates to an aqueous adhesive composition and a method of surface-treating a molded article using the same. Particularly, the adhesive composition may be a highly elastic aqueous adhesive composition, which may be eco-friendly by reducing of smell and VOC generation generated from an organic solvent. The adhesive composition may be prepared by steps comprising adding a water-dilutable polyurethane resin having a hydroxyl group to a waterborne polyurethane resin, thereby improving properties such as elastic recoverability and scratch resistance while satisfying conventional properties, and a method of surface-treating a molded article using the same.
(b) Background Art
A hard feeling of conventional vehicle interior plastic component surfaces has reduced value and does not properly satisfy consumers pursuing high-end products. Accordingly, in order to enhance emotional quality or texture of vehicle interior materials, outer sides of injection-molded articles have been covered with a variety of fabrics to enhance warm feeling. For example, surface treatment has been carried out by a method wherein workers tightly pull fabric such that injection-molded articles are covered, after spreading oil-based adhesive on outer sides of injection-molded articles.
However, in this case, cost burden may be high due to use of expensive fabric (e.g. suede), volatile organic compounds (VOCs) generated from an organic solvent contained in an oil-based adhesive may induce environmental pollution, and worker's health may be damaged due to strong smell.
In order to address such problems, vehicle companies have provided a VOC emission amount of a minimum requirement standard, and restriction may be reinforced by various environment-related regulations in South Korea and in other countries in the world.
In addition, waterborne polyurethane may be used as a water-based adhesive to enhance an oil-based adhesive. Waterborne polyurethane solubilizes both terminals thereof using isocyanate, a prepolymer having a urea group at both terminals thereof using polyvalent amine as a chain extender may be prepared through dispersion in water. However, reproduction and molecular weight control, upon dispersion, of waterborne polyurethane obtained according to the method may be difficult. Particularly, when the waterborne polyurethane is used as an adhesive, a film becomes soft, after curing, due to lack of a functional group that may induce curing reaction, thus film properties such as weather resistance, wear resistance, etc. may be negatively affected. Accordingly, use of the waterborne polyurethane as a water-soluble top coat (clear) for vehicles may not be desirable. In addition, the waterborne polyurethane has disadvantages such as difficult painting workability due to a large molecular weight and very hard characteristics.
In the related arts, Korean Patent No. 1161893 discloses an aqueous dispersion including a polyester-polyurethane resin dispersion and a hydroxy-functional aqueous or water-dilutable binder. However, a water dispersion process may be additionally performed.
In addition, Korean Patent No. 217448 discloses an aqueous solution or an aqueous dispersion of a water-dilutable organic polyol ingredient containing a mixture of a hydroxy-functional polymer and an aqueous binder composition containing a polyisocyanate ingredient. However, there is a disadvantage wherein the content of organic solvent in an aqueous dispersion may increase.
In addition, Korean Patent Application Pub. No. 2006-0052176 discloses an aqueous foam coating composition including an aqueous polyurethane-polyurea dispersion, a hydroxy-functional aqueous or water-dilutable binder, polyisocyanate, a foam and a stabilizer. However, a foaming process may be additionally performed and wear of a foam may be decreased.
Therefore, there is a need for development of a novel adhesive which may prevent environment pollution by decreasing use of an organic solvent and enhance properties such as texture, wear resistance, scratch resistance, etc., and a method of surface-treating a molded article using the same.
The above information disclosed in this Background section is only for enhancement of understanding the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.